In a typical cellular radio system, wireless terminals communicate via a radio access network, RAN, with one or more core networks. The wireless terminals can be mobile stations or other types of user equipment, UE, such as portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data with radio access network, e.g., mobile telephones and laptops with wireless capability.
The RAN covers a geographical area which is divided into cell areas, with each cell area or group of cell areas being served by a radio access node. A cell is a geographical area where radio coverage is provided by equipment at the radio access node. Each cell is identified by an identity within the local radio area. The radio access nodes communicate over the air interface with the UE within the cells served by the node.
The Universal Mobile Telecommunications System, UMTS, is a third generation mobile communication system, which evolved from the Global System for Mobile Communications, GSM, and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access, WCDMA, access technology. UTRAN is essentially a radio access network using wideband code division multiple access for user equipment units, UEs. The Third Generation Partnership Project, 3 GPP, has undertaken to evolve further the UTRAN and GSM based radio access network technologies. Specifications for the Evolved Universal Terrestrial Radio Access Network, E-UTRAN, are ongoing within the 3GPP. Another name used for E-UTRAN is the Long Term Evolution, LTE, Radio Access Network, RAN.
Long Term Evolution RAN is a 3GPP radio access technology wherein a flat architecture is used with a singled type of nodes connected directly to a core network. The LTE RAN comprises evolved radio access nodes, e.g., evolved NodeBs or eNodeBs or eNBs, providing evolved UTRA user-plane and control-plane protocol terminations toward the User Equipment, UE. The eNodeB is a logical node and not a physical implementation. A common implementation of an eNodeB is a three-sector site, where the eNodeB includes equipment for handling transmissions in three cells. However, other implementations can be found as well. The eNodeB hosts functions for radio resource management, mobility management and user plane functions, among others. The X2 interface connects eNodeBs to each other.
The eNodeB is connected to the core-network by means of the S1 interface. One eNodeB can be connected to multiple Mobility Management Entities. A Mobility Management Entity, MME, is the core network node responsible for mobility management, e.g., UE tracking and paging procedures.
Paging is used for network-initiated connection setup when the UE is in a Radio Resource Control idle mode, RRC_IDLE. In idle mode, the UE does not belong to a specific cell. No data transfer may take place as the UE is in idle mode, RRC_IDLE, most of the time in order to reduce battery consumption. User Equipment, UE, in the RRC_IDLE is periodically enabled to receive paging messages from the network.
Each time a UE attaches to the network, it also performs a Tracking Area Update, TAU, procedure and registers in a certain Tracking Area, TA. The Tracking Area represents a group of cells, preferably adjacent. Each eNodeB may handle radio transmission in cells belonging to different tracking areas. A Tracking Area List represents a group of Tracking Areas, thus including a higher number of cells than the Tracking Area. In response to the registration, the UE receives a Tracking Area List from the network and as long as the UE is present in one of the Tracking Areas within the Tracking Area List it does not have to perform a new TAU procedure.
In LTE, the mechanism for downlink data transmission on the Downlink Shared Channel, DL-SCH, is used for paging. The UE monitors control signaling for downlink scheduling assignments related to paging. The location of the UE in Idle Mode is not known on a cell level; thus, the paging message is typically transmitted across multiple cells. The MME initiates the paging procedure by sending a paging message to one or more eNodeBs. In LTE, an S1 paging message is sent from the MME to the eNodeB to request paging of a certain UE. In present LTE system, paging is escalated from an eNodeB level, to a Tracking Area, TA, level and finally to a Tracking Area List level.
The tracking area is controlled by the MME. Typically, the eNodeB in which the MME knows the UE to have been present last is first asked to perform the paging procedure (in all configured cells) a number of times. If no page response is received, the eNodeBs are secondly asked to perform the paging procedure in cells of the eNodeBs belonging to a Tracking Area, and last the eNodeBs are asked to perform the paging procedure in cells of the eNodeBs belonging to the Tracking Area List. However, if a TA is extensive, escalating from eNodeB level to Tracking Area level could imply an escalation from one eNodeB up to 100 eNodeBs or more involved in the page of one User Equipment, UE. Such escalation will incur a high paging load on the radio access network.
What is needed therefore, and an object of the technology described herein, is to provide solutions that reduces paging load in the network during an escalated paging procedure.